1. Field of the Invention
This invention relates to alkali metal alumino carbonates, their methods of preparation and areas of use, and more particularly, relates to novel amorphous and crystalline alkali metal alumino carbonate materials.
2. Description of the Prior Art
Crystalline sodium alumino carbonate is known to the prior art as the natural mineral Dawsonite. This crystalline product has the general structural formula as follows: EQU Na.sub.2 O:Al.sub.2 O.sub.3 :2CO.sub.2 :2H.sub.2 O
this material is a rare mineral which occurs naturally but has found limited utility.
U.S. Pat. No. 3,629,153 and corresponding French Pat. No. 1,573,310 relate to the preparation of alkalized alumina, which material is a solid absorbent prepared using Dawsonite as an intermediate material. The crystalline Dawsonite used in this patent is formed by the reaction of sodium aluminate with ammonium carbonate or carbon dioxide. The intermediate Dawsonite product is then heated at an elevated temperature to convert it to a granular alkalized alumina absorbent which is useful as an absorbent for gaseous materials.
A similar disclosure may be found in U.S. Pat. No. 2,992,884 which concerns a method for the removal of sulfur oxides from gases utilizing as the absorbent material an alumina product described as an alumina or chromium support having dispersed thereon an alkali metal oxide such as sodium oxide. This material is prepared by a reaction of an aluminum sulfate hydrate with sodium carbonate by adding an aqueous solution of the aluminum sulfate to an aqueous solution of the sodium carbonate at 90.degree. C. The mixture is then stirred mechanically, allowed to settle and the supernatant liquid decanted. The product is then heated to 600.degree. C. which reduces the carbon dioxide content.
A substantial amount of work has been carried out in the art for the preparation of alkali metal alumino silicates. Many of these materials are described as pigments or zeolites and have various particle sizes and other special properties. These materials are generally prepared by the reaction of alkali metal silicates and aluminum salts by mixing of the two solutions to form the precipitate. One basic patent in this area is U.S. Pat. No. 2,739,073 to Bertorelli, assigned to the Applicant's assignee, which discloses procedures for the preparation of finely divided alkali metal alumino silicates by the reaction of alkali metal silicates and aluminum salts.
To Applicant's knowledge however, there is no disclosure in the art for the preparation of amorphous alkali metal alumino carbonates or for the crystalline alkali metal alumino carbonates prepared in the manner described herein. Accordingly, the present invention concerns an advance in the art in the preparation of these products and in provision of a novel amorphous alkali metal alumino carbonate.